Note: Descriptions are shown in the official language in which they were submitted.
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The present inven-tion relates to a gate assembly
haviny a vertical ga-te pole, a gate pivotable about and ver-ti-
cally displaceable along said pole, and a mechanism for auto-
matically opening and closiny the date comprising a gate-
suppor-ting roller which rests on a stationary cam -track having
a lowermost point which determines a res-t position of the yate
correspondiny to the closed position thereof, said track climbiny
on at leas-t one side of said point in order that the yate when
swuny from the closed position shall be returned by yravity to
the closed position by the support roller rolliny down the cam
track, an abutment which is movable between a position obstructing
the path of the support roller along the cam track, in which
position it allows movement of the support roller over the abut-
ment in a direction away from the rest position but prevents the
support roller from returning to the rest position, and another
position in which the abutment to a ma~or part is removed from
the path of the support roller in order to allow the support
roller to return along the cam track to the rest position.
GB-A-481,285 describes a gate assembly of the type
referred to wherein the gate is swung to opened position by ::
being pushed out of the way by a vehicle which presses against
the gate, and then automatically swinys back to the closed
position thereof when the vehicle has passed throuyh the gate
openiny. In this prior art yate assembly the abutment comprises
a pivoted cam. During the opening movement of the gate the
roller moves on-to the cam from one side of the pivot axis thereof .
and then the cam pivots when the gate is substan-tially in a
~S pOSitiOII to .Illow the roller to move downwards alony the cam
at the other side of the pivot axis, the yate thereby moviny to
opened position. Then, the yate returns to the closed position,
the abutment beiny displaced from the path of the roller.
A drawback of -this prior art yate is that it re-turns
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tso rapidly to th~ closed position thereof so that there is a
risk that the vehicle passing through the gate opening rubs the
slde ayainst the gate whereby the gate can yet caught on the
vehicle or can cause damage thereon.
For the purpose of eliminating this drawback and pro-
~iding a gate with delayed return in order that the gate shall
remain in the opened position during the time necessary for the
vehicle to pass through the gate opening, the invention provides
a gate assembly o~ the type referred to above characterized by
spring means having a damper allowing the abutment to be slowly
removed from the path of the support roller along the cam track
against the spring bias under the pressure of the support roller
against the abutment and to be rapidly returned by the spring
bia,s to the position in which it obstructs the path of the
support roller along the cam track when the roller has passed
the abutment.
In order to illustrate the invention, an embodiment
thereof will be described in more detail below with reference
to the accompanying.drawing in which
FigO 1 i6 a side view of a gate arranged according
to the invention, and ~
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FIG. 2 is an enlarged perspective view of the
arrangement according to the invention.
The gate of FIG. 1 comprises a tube construction
10 which is journalled by mean~ of a vertical tube 11
on a gate pole 12. The gate has vertical tubes 13
suitably spaced in order that a vehicle which moves
towards the gate shall hit the gate with the bumper
thereof at these tubes and push the gate out of the
way from the closed position ~hereof when the vehicle
is moving through the gate opening.
As will be seen from FIG. 2, the gate tube 11 is
journalled on the tubular gate pole 12 by means of
bushings 14 which can be provided at top and bottom in
the tube 11 and possibly at one or more positions
therebetween. The gate tube 11 is not only pivoting but
also displaceable vertically on the gate pole 12, and
one or more grease fittings 15 are provided for lubricat- ¦~
ing the bearings between the gate tube and the gate
pole 50 that the gate tube runs easily on the gate pole.
At the top, the gate tube 11 is closed by a cover 16
which can be secured by means of a lock bolt 17 or the
like. i~-
On the inner side of th~ gate tube 11 there is
pivotally mounted a support roller 18 formed as a ball
bearing roller with a trunnion 19 secured by a screw
connection 20 to the gate tube. The screw connection is
covered externally by a metal sheet casing 21. The
support roller 18 is received by an opening 22 in the
gate pole 12, and the lower edge of this opening forms
a cam track 23 climbing progressively in the direction
of the arrow 24 from the position of the support roller
18, shown to the right in FIG. 2. Said position of the
support roller 18 corresponds to the closed position
of the gate 10. ,
Inside the gate pole a tubular element 25 is
mounted for axial displacement, and this element is
non-rotatably guided by m~ans of an axiallv extending
rib 26 fixedly arranged inside the gate pole 12. By
means of a bracket 27 having a socket 28 at the outer
end thereof the element 25 is secured to the piston
rod 29 of a hydraulic ram 30 by means of a screw
connection 31, and the ram 30 is connected at the
upper end thereof to a ring or plate 32 which in turn
ls secured to the gate pole 12 by means of a screw
connection 33. The hydraulic ram 30 is of the type
(shock absorber) having a spring which biases the
piston of the hydraulic ram in one direction which is
assumed to correspond in the present case to dis~lace-
ment of the piston rod 29 in upward direction. Further-
more, the piston of the hydraulic ram 30 has a valvecontrolled connection between the cylinder spaces
filled with hydraulic fluid on each side of the piston,
said connection being of the kind allowing fluid to
pass between the opposite sides oE the piston when the
piston is displaced upwardly under the bias of the
spring while the flow of the fluitl is choked when the
piston is displaced downwardly in the cylinder against
the bias of the spring.
The element 25 forms a crest 34 having a gently
sloping ramp 35 and a steeper ramp 36, and under the
bias of the spring in the hydraulic ram 30 this crest
is located in the path of the support roller 18 along
the cam track 23 as is shown in FIG. 2, the crest 34
projecting upwardly from the cam track 23 as a nose.
The crest is kept in this position by the spring and
it can be depressed from said position by a slow
motion only against the bias of the spring because
the choked flow of hydraulic fluid between the opposite
sides of the piston retards such depression. The piston
has a stroke which is large enough for the crest to be
depressed sufficiently to a position wherein it is
flush with the cam track ~3, or at least to a position
wherein the crest projects slightly from this cam
track. However, when the pressure against the crest 34
is relie~ed, the crest will rapidly return to the
position shown under the bias of the spring in the
hydraulic ram 30 because the fluid can then pass
rapidly from one side of the piston to the other side
thereof.
If the gate is swung towards opened position
according to the arrow in FIG. 1 by a vehicle being
driven against the gate and pushing this out of the
way, this means that the support roller 1~ rolls in
the direction of the arrow 24, the roller being lifted
from tha cam track 23 when it is rolling upwards the
ramp 36 on the crest 34 in order to roll thereafter
onto the cam track 23 again along the ramp 35. During
this movement the gate i5 thus lifted, the gate tube
11 being displaced vertically on the gate pole 12, and
since the oil in the hydraulic ram 30 by the choking
action in the valve controlled opening in the piston
retards the movement downwards of the crest 34, this
crest will not be depressed when the support roller
18 is moving over same. Some small depression may of
course occur at the passage of the roller but it is
of no significance. The support roller 18 will be
caught by the crest 34 at the side of the crest where
the ramp 35 is provided, and will now be in the
position 18' as indicated by ~ash and dot lines, in
which the gate is fully opened and thus is swung
substantially 90 or preferably more than 90 from the
position shown in FIG. 1. Having passed the top of the
crest 34 the support roller 18 will roll down the ramp
35 under the weight of the gate so that the gate as a
consequence thereof will be swung automa-tically to
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opened position without the vehicle pushing against
the gate. This automatic swinging can begin in a 45
to 60 position of the gate. Resting against the cam
track 23 and against the ramp 35 the support roller 18
will cause a pressure against the crest 34 in the
position 18l, said pressure being dependent on the
weight of the gate, and ~he crest will then move
slowly downwards against the bias of the spring
provided in the ram 30, as allowed by the flow of
hydraulic fluid between the two sides of the piston
through the cho~ed opening therein. Eventually, th~
crest 34 will reach a position in which the support
roller 18 can roll along the cam track 23 back to the
position shown by solid lines in FIG. 2. By adapting
the choking in the piston and the inclination angles
; of the cam track 23 and the ramp 36 in a suitable way
in relation to the weight of the gate it is possible
to adapt, as desired, the time it takes for the gate
to depress the crest 34 when the gate is in the opened
position in order that the gate shall then be able to
swing to the closed position thereof. As soon as the
support roller 18 has passed the depressed crest 34
when the gate is moving from opened position to closed
position the spring of the hydraulic ram 30 will
rapidly press the crest 34 upwards to the position
shown because such movement is not prevented to a
significant extent by the fluid in the hydraulic ram.
Then the gate is ready to be opened again in the manner
described.
Thus, it will be seen that by the arrangement
according to the inven-tion the gate will be swung
automatically to the opened position when such movement
has been initiated by a vehicle moving against the gate
and pushing it out of the way, and the gate will also
be securely retained in the opened position thereof in
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order that the gate shall return after a delay to the
closed position thereof. Moreover, it is possible to
adapt the delay in such a manner that the gate will be
; maintained in the opened position long enough for a
vehicle of maximum length to pass through the gate
opening at a low speed.
As described above, the arrangement allows the
gate to be swung towards one side only, but of course
it is possible to provide the element 25 with two
diametrically opposite crests 34 and to make the
opening 22 in the gate pole sufficiently large so that
the gate can be swung towards one side or the other
from a rest position in which the gate is closed and
will be retained for delayed return independently of the
gate being swung towards one side or the other. The same
element 25 and the same hydraulic ram 30 can control the
delay towards bcth sides.
The invention is not, of course, limited to the
embodiment shown but can be designed in other ways
within the scope of the accompanying claims. This is
true e.g. for the arrangement of the hydraulic ram 30
which is shown in a suspended position but can be
arranged also in a standing position inside the gate
pole 12. It is also possible to let the ram 30 move
together with the element 25 while the piston rod 29
is fixedly secured to the gate pole 12~ Moreover, the
element 25 can be arranged in different ways but the
tubular embodiment shown herein would be preferred con~
sidering that the eleme~t thereby can be guided in a
relatively simple manner. The spring can be arranged
outside the cylinder instead of being located inside
the cylinder as has been said to be the case in the `
embodiment shown.
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